The present invention relates to cellulose fiber having homogeneous physical property, in particular cellulose fiber for using as industrial materials, preferably tire-cord produced as following steps: preparing a homogeneous cellulose solution by swelling a cellulose powder with a concentrated liquid N-methyl morpholine N-oxide (NMMO); extruded-spinning the cellulose solution through an air gap using a spinning nozzle with 500 to 2000 of orifices and then obtaining a multi-filaments after solidifying the spun cellulose solution; and winding the multi-filaments after water-washing, drying and treating with a finishing oil.
In particular, the present invention relates to cellulose fiber having 500 to 2000 filaments, and is characterized in that the strength of multi-filaments is 4 to 9 g/d, the breaking elongation is 4 to 15% and the multi-filaments have homogeneous physical properties. More specifically, the present invention relates to the cellulose multi-filaments for use of industrial materials, in which each 100 mono-filaments selected from each three parts divided from the multi-filaments have the properties as following; a) 3 to 9 g/d in average, 7 to 15% in average breaking elongation and 0.035 to 0.055 in average birefringence, b) the differences of three parts in average strength, breaking elongation and denier are below 1.0 g/d, 1.5% and 0.7 denier, respectively, c) CV (coefficient of variation) (%) of three parts in average strength, breaking elongation and denier is below 10%, and d) the differences of the average birefringence of three parts are below 0.004.
A cellulose fiber manufactured with cellulose and NMMO is utilized in various fields needing the cellulose fiber in the process of manufacturing, because all the solvent used in the process of manufacture of the cellulose fiber is recycled and therefore the manufacture of the cellulose fiber corresponds to a non-pollution process, and the produced fiber has high mechanical strength, and referring to EPO no. 0356419 a cellulose solution produced using amine oxide together with NMMO is described, and U.S. Pat. No. 4,246,221 discloses a method for producing a cellulose solution with a tertiary amine oxide, and according to the above U.S. Pat. No. 4,246,221 the cellulose solution is spun using a device for forming such as a spinneret as filaments and then the filaments are precipitated in a bath to pass a coagulating bath and finally the swollen cellulose containing water is produced. But the above method takes a long time from dissolving to spinning, and the degradation of physical properties results from the long time. And also the expense of energy is so much that the cost for manufacturing is non-avoidable.
On the other hand, H. Chanzy et al. produced a cellulose fiber with 56.7 cN/tex of strength and 4% of breaking elongation in a manner that a cellulose solution which a DP 5,000 of cellulose was dissolved by NMMO and ammonium chloride or calcium chloride was added and the resultant was spun through an air gap, but the method for producing the cellulose fiber has difficulty with being available commercially because the number of filament is only 1 strand and the fibril orientated in direction of axis is exfoliated.
Referring to other prior invention, U.S. Pat. No. 5,942,327 describes a cellulose fiber having 50 to 80 cN/tex (5.7 to 9.1 g/d) of strength, 6 to 25% of elongation and 1.5 dtex of mono strand fineness and produced in a manner that a aqueous NMMO solution into which DP 1,360 of cellulose is dissolved is spun through an air gap, but the number of filaments is only 50 strands. The cellulose fiber produced in the above manner has difficulty with being available commercially, considering that generally the number of filaments for using as industrial materials should be about 1000 strands (1,500 denier) because (a) the efficient remove of solvent is necessary in view of process and (b) the capacity of inner skin is enough maximized to resist the repeated fatigue in view of physical property.
In general when a spinning process is performed, in view of technology to spin with 500 to 2,000 of orifices per spinning nozzle is more difficult than to spin with 50 orifices per spinning nozzle. The reason is why that the adjustment of spinning pressure is more difficult in proportion to the increase of the number of orifices and thus it is difficult to design a spinning nozzle and a distributing plate, in particular to adjust the condition for cooling evenly in an air gap and for washing and drying homogeneously all the filaments of 500 to 2,000, and as result it is very difficult to make all the filaments posses physical properties above a certain level and the homogeneous physical properties, and therefore the physical properties of 50 strands according to U.S. Pat. No. 5,942,327 is not sufficient for reference to the application of industrial materials.
In particular, because the increase of the number of filaments affects the stability of process relating to adhesion to the filaments spun from the nozzle and the efficiency when a spinning is performed through an air gap, the number of holes in a distributing plate for dispersing evenly the cellulose solution on the nozzle, the space of the holes and the diameter of the holes as well as the outer diameter of the nozzle and the diameter and space of orifices are very important.
As described in the above, as the number of filaments increases a new design for spinning is necessary considering the length of air gap, the blowing condition of cooling air, the direction of the coagulating solution and the spinning speed, and the physical properties may be different according to the design.
U.S. Pat. No. 5,252,284 describes a cellulose fiber having 800 to 1,900 of filaments, however, from the spinning condition that air gap below 10 mm is too short and spinning speed, 45 m/min is too slow reveals that the 15.4% of elongation is sufficiently high, but the 47.8 cN/tex (5.3 g/d) of strength is not sufficient for use of a industrial material, in particular tire-cord and also the cellulose has disadvantage that the physical properties of each filament are not homogeneous.